Covalent Bonds

What is the Octet Rule? All atoms are trying to have full outshells XS 2 XP 6 configuration They want 8 electrons

What is covalent bonding?

Covalent Bonds Involve sharing outer energy level electrons.

How Are They Different Than Ionic? Ionic bonds work by electromagnetic attraction. A positively charged ion is attracted to a negative ion. Covalent bonds work by sharing electrons. They do not have charges, but are hard to separate due to this sharing.

Cl How will two chlorine atoms react?

Cl Each chlorine atom wants to gain one electron to achieve an octet

Cl

octet

Cl circle the electrons for each atom that completes their octets octet

Cl circle the electrons for each atom that completes their octets The octet is achieved by each atom sharing the electron pair in the middle

Cl circle the electrons for each atom that completes their octets The octet is achieved by each atom sharing the electron pair in the middle

Cl circle the electrons for each atom that completes their octets This is the bonding pair

Cl circle the electrons for each atom that completes their octets Single bonds are abbreviated with a dash

Cl circle the electrons for each atom that completes their octets This is the chlorine molecule, Cl 2

Lets keep track of the little numbers! What does the superscript number mean? Charge What does the subscripts number mean? Number of atoms in a bond

Stop here We will finish this PowerPoint at a later time

Covalent Bonds Each oxygen has 6 valence electrons and wants two more to have a full octet. 6 electrons

Covalent Bonds If one oxygen shares two electrons with the other, the other has a full octet. 8 electrons – happy!4 electrons left

Covalent Bonds But, then the other oxygen is short, so it pulls them back. Now the other oxygen shares 2 electrons 4 electrons left8 electrons – happy!

Covalent Bonds Thus, by each of them sharing two electrons back and forth, they both are at the full octet simultaneously. 8 electrons

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O O Both electron pairs are shared.

O O We call this a double bond!

So Who Covalently Bonds? Alkali or Alkaline Earth Metals do not form covalent bonds! Metals do not form covalent bonds. Only nonmetals

Electron Distribution C.... Electrons occur in 4 fours separated as far apart as possible Valence Electrons: 4

Electron Distribution N... C.... Electrons occur in 4 fours separated as far apart as possible Valence Electrons: 4 5

Electron Distribution N... C O Electrons occur in 4 fours separated as far apart as possible Valence Electrons: 4 5 6

Single Bond Ethane is C 2 H 6

Double Bond Ethene is C 2 H 4

Triple Bond Acetylene is C 2 H 2

Quadruple Bond??? Cannot occur, because the last bond can not bend all the way around. Too far to bend Especially since triple bonds are so rigid

Possible Covalent Bonds Only where single electrons are located, can covalent bonds be made. Carbon has 4 single electrons, thus it can make 4 bonds. Nitrogen has 3 single electrons, thus it can make 3 bonds. Oxygen has 2 single electrons, thus it can make 2 bonds.

Double Bonds Revisited Since Oxygen can make two bonds, and Carbon can make four, it makes for some interesting combinations.

Why Carbon is the Key to Life It is precisely because carbon can make 4 bonds, as well as, double and triple bonds, that makes it so critical to life. Carbon chains can form virtually every formation possible.

DNA and the building blocks for life Carbon, plus two other flexible elements, oxygen and nitrogen form the backbone of DNA DNA contains the genetic code for the building of life out of the largest of all molecules, proteins.

Proteins are the largest molecules known

Resonance Bonding The ability of electrons and bonds to alternate back and forth between different atoms. Occurs when there is more than one possible structure that can exist with covalent bonds. Resonance bonds are drawn as dashed lines.

Content Objectives SWBAT describe the process by which two or more atoms share electrons in order for each to achieve the Octet Rule.

Electron Distribution N... C O Electrons occur in 4 fours separated as far apart as possible Secret Question: Why do electrons first fill orbitals one at a time before pairing up? Valence Electrons: 4 5 6

Electron Distribution N... C O Electrons occur in 4 fours separated as far apart as possible Secret Question: Why do electrons first fill orbitals one at a time before pairing up? It is because electrons repel each other and want to be as far apart as possible. Valence Electrons: 4 5 6

Exception to Octet Rule Boron only has 3 valence electrons, so it is impossible to get to eight via covalent bonding Without 4 valence electrons, the shape of the molecule flattens out. B... BH 3